1. Field of the Invention
The present invention relates in general to jet engines capable of operating either as a turbofan or as a ramjet and relates in particular to an assembly which mixes core engine exhaust flow with bypass air flow during turbofan operation and which isolates the engine turbomachinery from bypass air flow during ramjet operation.
2. Description of Prior Developments
In order to efficiently operate aircraft jet engines at both lower and higher Mach numbers, aircraft engine designers have combined gas turbine engine features with ramjet engine features as shown, for example, in U.S. Pat. Nos. 3,153,904, 3,324,660 and 3,635,029. Current studies for advanced air breathing engines indicate the need for jet engines capable of flight in the Mach 4 to 6 range. At Mach numbers less than about 3, such engines typically operate in a turbofan mode while, at higher Mach numbers, they generally operate as a ramjet.
A flow control assembly is required that will easily allow the engine to transition between turbofan operation and ramjet operation. Such an assembly should provide for thorough mixing of bypass air and core engine exhaust gases during turbofan or core engine operation in order to ensure efficient combustion in the augmenter or afterburner. The assembly should also block inlet airflow through the core engine during ramjet operation so that virtually all inlet air is available for ramjet combustion.